Antifluorescein antibodies and partial protein constructs are being examined in order to isolate the primary conformational states and estimate the magnitude of the conformational substates involved in antibody-hapten interactions. A variety of monoclonal anti-heme antibodies will be examined spectroscopically to characterize the affinity to different porphyrin and heme groups. These measurements will include fluorescence polarization, steady-state fluorescence and CD-measurements. Using different porphyrins as haptens will allow us to determine the antigenic group for each Mab.